1. Field of the Invention
The present invention relates to a medical device that is used to cut a cornea.
2. Background Information
There have been developed a number of different surgical techniques to correct hyperopic or myopic conditions of a human eye. U.S. Pat. No. 4,840,175 issued to Peyman discloses a procedure wherein a thin layer of a cornea is cut to expose the stroma layer of the cornea. A laser beam is then directed onto the exposed corneal tissue in a predetermined pattern. The laser beam ablates corneal tissue and changes the curvature of the eye. This procedure is sometimes referred to as Laser in situ Keratomileusis (LASIK).
U.S. Pat. No. Re 35,421 issued to Ruiz et al. discloses a device for cutting a cornea in a LASIK procedure. Such a device is commonly referred to as a microkeratome. The Ruiz microkeratome includes a ring that is placed onto a cornea and a blade that is located within an opening of the ring. The device also contains a drive mechanism which moves the blade across the cornea in a first direction while the blade moves in a reciprocating transverse direction to cut the eye. The device can create a lamella flap of the cornea which is flipped back so that the stromal bed of the cornea can be ablated with a laser.
U.S. Pat. No. 6,051,009 issued to Hellenkamp et al. discloses a microkeratome that is sold under the trademark HANSATOME. The HANSATOME microkeratome moves the blade in an arcuate path about the cornea. The HANSATOME includes a disposable blade assembly that can be loaded and removed from the device. The blade assembly includes a blade holder that is attached to a cutting blade. The blade holder has a recess that receives the end of a drive shaft. Rotation of the output shaft moves the blade in an arcuate path, and moves the blade in a back and forth motion to create the lamella flap of the cornea.
Microkeratomes have three primary components, a hand piece that contains a motor, a head that holds the blade, and a ring that applies a suction to maintain the position of the microkeratome relative to the cornea. Because the microkeratome is in contact with patient tissue it must be cleaned after each procedure, typically in an autoclave. The motor and accompanying gears are typically enclosed by a housing of the hand piece. The enclosed nature of the assembly increases the difficulty of cleaning the internal components of the hand piece. Additionally, the autoclave process may degrade the hand piece motor after a number of procedures and cleaning cycles. It would be desirable to provide a microkeratome that does not require the hand piece to be sterilized after each surgical procedure.
The blades used to cut tissue are replaced after each procedure. The replacement blades are typically loaded into the head of the microkeratome with a pair of tweezers. The blade must be loaded accurately so that a drive pin of the motor assembly is inserted into a corresponding slot of a blade holder. Accurately loading the blade with tweezers can be a time consuming process. It would be desirable to provide a blade package that can be used to accurately load a blade into a microkeratome in a time efficient manner.
A complication may occur while the microkeratome is cutting the lamella flap. It may be desirable to remove the microkeratome in the middle of a cut. Removing the microkeratome requires releasing the vacuum of the suction ring. Releasing the vacuum allows the cornea to move back to its original shape. Movement of the cornea will also cause the blade to move. Movement of the blade may cause damage to the cornea. It would be desirable to provide a microkeratome that allows a surgeon to remove a blade while the suction ring is still fixed to the cornea. It would also be desirable to provide a microkeratome that allows the surgeon to vary the thickness of the lamella flap hinge.